Study On The Phase Equilibrium In Extraction Process Of Aromatics Based On Molecular Simulation

As one of the most basic raw materials in the petrochemical field,aromatics play a huge role in industries such as manufacturing,construction,pharmaceuticals and pesticides.Aromatics extraction is an important technology for obtaining aromatic products with high purity.Aromatics extraction technology has the advantages of high processing capacity,operational safety and economic efficiency,and is widely used in actual industrial production.Phase equilibrium data are critical for the extraction of aromatics.However,some phase equilibrium data on the extraction of aromatics are still missing and not publicly available.Therefore,study on the phase equilibrium of aromatics extraction processes has vital practical significance.In this research,the LLE data of the non-aromatic-aromatic-sulfolane ternary system were collected,measured,and predicted based on the actual data from the extraction of aromatics using sulfolane.And the mechanism in extraction of aromatics using sulfolane was explored.LLE data of cyclopentane-benzene-sulfolane and 3-methylpentane-benzene-sulfolane were measured at 40℃and 101.3 k Pa.The experimental LLE data were examined using the Hand and Othmer-Tobias equations,where the correlation coefficients(R~2)were close to unity,indicating the reliability of the experimental data.The LLE data for the extraction of aromatics using sulfolane were predicted using COSMO-RS model with the help of molecular simulation.The root mean square deviation(RMSD)between predicted data and experimental(reference)data ranged from 0.0334 to 0.0898,indicating that the COSMO-RS model can better predict the LLE data for the extraction of aromatic using sulfolane.In addition,the interactions between sulfolane and aromatics(non-aromatics)were analyzed by quantum chemistry calculation.The results show that the weak hydrogen bonds and van der Waals interactions between sulfolane and aromatics were responsible for the extraction of aromatics using solufolane.Secondly,the LLE data for the extraction of aromatics using sulfolane predicted by the COSMO-RS method using the NRTL and UNIQUAC thermodynamic model were subjected to correlation analysis,and relevant parmeters of the model were determined and the relevant binary interaction parameters were obtained.From the correlation results,the RMSD of the data calculated using the NRTL and UNIQUAC models and the predicted data were in the range from 0.0007 to 0.0180,indicating that the two thermodynamic models can be better used to correlate the predicted liquid-liquid equilibrium data by COSMO-RS,and also indicating that the two models are suitable for the extraction computational study of aromatics using sulfolane.Finally,the binary interaction parameters obtained from the regression analysis were applied to model the extraction full-process modeling of aromatics using sulfolane.The simulation results showed that the mass fraction of the final benzene product was99.97%,which meets the industrial requirements(mass fraction≥99.8%).The main process indicators of the extraction column and raffinate oil washing column were close to the actual industrial data,and the maximum relative deviation was 4.27%,and the relative deviations between the simulated and actual values of the key components at the top and bottom of the tower were within 3.70%.Therefore,the obtained parameters can be better applied to the extraction process of aromatics using sulfolane,and simulation results were reliable.In conclusion,it is feasible to predict the phase equilibrium data of the aromatics extraction system using molecular simulation,and the simulation results can reliably guide the extraction process of aromatics using sulfolane.